Immunoassay test strips are well known devices for measuring concentrations of substances found in biological liquids. Typically, a user will deposit a test sample of the biological liquid on a sample receiving pad either in fluid communication with the test strip, or forming a portion of the test strip. The biological liquid sample is permitted to wick along the test strip to a predefined testing area that includes a reagent capable of a readable change when contacted by a predetermined constituent in the test sample, such as by changing color.
For purposes of this disclosure, test strips will be described in relation to glucose (HbA1c) testing for those afflicted with diabetes. However, test strips are also commonly used for many other purposes, such as drug use testing, pregnancy (hCG level) testing, or pH testing.
For HbA1c testing, a user deposits a sample of blood, which may be diluted, on the sample receiving pad associated with the test strip. The blood then wicks along the test strip to the reagent area where a color change may occur. The degree of the color change or the color itself is correlated to a concentration of HbA1c in the test sample. Similarly, the absence of a color change indicates that the level of HbA1c is below that which is detectable by the particular strip.
Some test strips can be read by a human eye while others require sophisticated equipment, such as a spectrophotometer capable of reading reflectance values. It is necessary that such spectrophotometers be as accurate as possible. For those with diabetes, entire treatment protocols may be established or adjusted based on the level of HbA1c found in the blood at a particular time.
Many factors affect the accuracy of test strips. In the glucose testing area, it is well known that temperature and viscosity play important roles. Test meters may therefore be calibrated, which is often referred to as “compensated,” for these factors. Existing methods of compensating are known.